1. Field of the Invention
The present invention relates to a touch panel, and more particularly to a touch panel apparatus and method for controlling the same capable of preventing touching error due to double touching.
2. Description of the Related Art
With respect to a display representing pictures, there are a cathode ray tube, a liquid crystal display, a plasma display panel, and an electro-luminescence display, and so on. In order to input information with ease on the screen, if the user presses the surface with a pen or a finger, such a display is used as an input device by setting on the screen surface a touch panel inputting information corresponding to touching position.
FIG. 1 is a diagram illustrating a touch panel apparatus according to the related art. Referring to FIG. 1, the conventional touch panel apparatus comprises a touch panel 10 for providing the coordinate signal of a touch point, and a touch panel controller 30 for controlling the driving of the touch panel 10 and computing the coordinate value in accordance with the coordinate signal from the touch panel 10 and providing it to a system 40.
The touch panel 10 includes an upper film 12 having a first transparent conductive layer formed thereon, and a lower substrate 16 separated from the upper film 12 and having a second transparent conductive layer 18 formed thereon.
The upper film 12 and the lower substrate 16 are joined by a sealant 22 spread along a non-touch region, specifically the peripheral region, and are thus separated by the height of the sealant 22. Further, for separation of the upper film 12 and the lower substrate 16 in the touch region, a plurality of dot spacers 20 are formed on the first transparent conductive layer 14 of the upper film 12 or the second transparent conductive layer 18 of the lower substrate 16.
A transparent film using the polyethylene terephthalate (PET) is mainly used as the contact material for pressing on the upper film 12 with a pen or a finger. The same material used for the upper substrate is also for the lower substrate 16. A similar material like a glass substrate or plastic substrate may be also used. Transparent conductive materials like Indium-Tin-Oxide (ITO), Indium-Zine-Oxide (IZO), and Indium-Tin-Zine-Oxide (ITZO) are used for the first and the second transparent conductive layer 14 and 18.
The touch panel 10 further comprises an X-electrode bar 15 connected to the both sides of X-axis direction of the first transparent conductive layer 14 and a Y-electrode bar 19 connected to the both sides of Y-axis direction of the second transparent conductive layer 18. The X-electrode bar 15 has a first X-electrode bar 15A supplying the driving voltage (Vcc) and a second X-electrode bar 15B supplying the ground voltage (GND) so that the current may flow along the X-direction in the first transparent conductive layer 14. The Y-electrode bar 19 has a first Y-electrode bar 19A supplying the driving voltage (Vcc) and a second Y-electrode bar 19B supplying the ground voltage (GND) so that the current may flow along the Y-axis direction in the second transparent conductive layer 16.
When the pen or the finger presses the upper film 12, the first transparent conductive layer 14 is contacted with the second transparent conductive layer 18, and the touch panel generates the current signal or the voltage signal where the resistance is different in accordance with the touch location. The coordinate signal of the current or the voltage changed in accordance with the touch location is output as X-axis coordinate signal through the second X-electrode bar 15B connected to the first transparent conductive layer 14, and is output as Y-axis coordinate signal through the second Y-electrode bar 19B connected to the second transparent conductive layer 18. Here the touch panel 10 outputs sequentially the X-axis coordinate signal and Y-axis coordinate signal by control of a touch panel controller 30.
The generation of the coordinate signal is explained more fully hereinafter. If each of the driving voltage (Vcc) and the ground voltage (GND) is supplied to the X-electrode bar 15 through a first and a second switches 24 and 26 respectively, the touch panel 10 outputs the X-axis coordinate signal through the second X-electrode bar 15B in response to the resistance value changed by the point where the first and the second transparent conductive layer 14 and 18 are contacted. Subsequently, if each of the driving voltage (Vcc) and the ground voltage (GND) is supplied to the Y-electrode bar 19 through a first and a second switches 24 and 26 respectively, the touch panel 10 outputs the Y-axis coordinate signal through the second Y-electrode bar 19B in response to the resistance value changed by the point where the first and the second transparent conductive layer 14 and 18 are contacted. For this purpose, the first switch 24 supplies the driving voltage (Vcc) to either the first X-electrode bar 15A or the first Y-electrode bar 19A in response to the control signal (CS) from the touch panel controller 30 and the second switch 26 supplies the ground voltage (GND) to either the second X-electrode bar 15B or the second Y-electrode bar 19B in response to the control signal (CS) from the touch panel controller 30.
The touch panel controller 30 computes the coordinate value in accordance with the X-axis coordinate signal and the Y-axis coordinate signal of the touch point supplied from the touch panel 10 and supplies it to the system 40. Moreover, the touch panel controller 30 controls the first and the second switches 24 and 26 in accordance with the X-axis and Y-axis coordinate modes respectively and controls power supply (Vcc, GND) of the touch panel 10. For this purpose, the touch panel controller 30 includes an analog/digital converter 32 (hereinafter referred to as “ADC”) for converting the X-axis and Y-axis coordinate signals from the touch panel 10 to the digital data, a microcomputer 34 for computing the coordinate value by the combination of X-axis and Y-axis coordinate data from the ADC 32 and outputting it to system 40, an interface part 36 for relaying the coordinate value from microcomputer 34 and supplying it to the system 40. The ADC 32 converts each the X-axis coordinate signal and the Y-axis coordinate signal supplied sequentially from the touch panel 10 into the digital data to provide it to the microcomputer 34. The microcomputer 34 combines the X-axis and the Y-axis coordinate data supplied sequentially from the ADC 32, computes the coordinate value corresponding to the touch location of the touch panel 10, and then supplies the computed value to the system 40 through the interface part 36. Further, the microcomputer 34 generates the control signal (CS) every fixed period of time and controls the first switch 24 and the second switch 26.
The system 40 perceives the coordinate value supplied from the touch panel controller 30, executes its corresponding instructions by the coordinate value or operates the application program related with it. Further, the system 40 supplies a necessary power source signal and video data to the display (not shown) mounted on the surface of the touch panel 10.
The touch panel as described above executes the instructions corresponding to the coordinate value in the system 40 by means of detecting the coordinate value pressed by the pen or finger and transmitting it to the system. However, in the touch panel 10 double touching with the palm in conjunction with the pen or the finger may occur frequently. If such double touching occurs, it is difficult to detect exactly the real touch location corresponding to the pen or the finger location.
FIG. 2 is a diagram illustrating a double touching event on a touch panel according to the related art. As depicted in FIG. 2, when the touch panel 10 is doubly touched by the user's palm in conjunction with the pen, both of the pen touch point (PT) and the hand touch point (HT) are detected in touch panel 10. In this case, the pen touch point (PT) and the hand touch point (HT) may occur at the same time or occur within fixed time difference. When the pen touch point (PT) and the hand touch point (HT) occur at the same time, the touch panel 10 generates the coordinate signal of the middle position between two points (PT, HT). If the coordinate signal of the middle position is provided to the touch panel controller 30, each of the touch panel controller 30 and the system 40 recognizes erroneously the middle position as the pen touch point. On the contrary, if a hand touch point (HT) occurs subsequently to the pen touch point (PT), the touch panel 10 generates a first coordinate signal for the pen touch point (PT) at the position where the pen touches the panel, and then a second coordinate signal occurs at the middle position between the pen touch point (PT) and the hand touch point (HT). As described above, if the first coordinate signal corresponding to the real touch point and the second coordinate signal corresponding to the middle position of the double touching by the hand are inputted to the touch panel controller 30 sequentially, in case that the first and the second coordinate signal occur within the fixed time, for example 3.4 ms, the touch panel controller 30 computes the coordinate value for the second coordinate signal inputted later and supplies the second coordinate signal to the system 40. In this case, the system 40 recognizes erroneously the middle position of the double touching as the pen touch point (PT).
As described above, one important reason why double touching occurs often is associated with the force applied to the touch panel 10. Specifically, the value of the force recognized as a valid touch, more specifically the activation force (AF) is set to have small value. The activation force (AF) is defined in accordance with Equation 1:AF=ρH/L  (1)
wherein ρ is a constant thickness of a material of the upper film 12, and ‘H’ and ‘L’, as depicted in FIG. 3, are respectively the height of the spacer 20, and the pitch between adjacent spacers respectively.
Referring to the Equation 1, the activation force (AF) can be adjusted in accordance with the height and the thickness of the spacers 20, and the material characteristic of the upper film 12.
In general although the activation force (AF) of the touch panel 10 is set around 30 g˜80 g in order to improve the touch perception, the activation force having this amount, as described above, leads to double touching. In order to reduce the occurrence of double touching, the touch panel 10 is fabricated with a reinforced activation force (AF) of more than 150 g. But if the activation force is increased to more than 150 g, since the touching force accordingly, touching of panel 10 becomes a difficult operation.